The present invention relates generally to exclusion seals and more particularly to various forms of so-called cassette seals often used in automotive and other applications. In particular, the invention relates to a simple and reliable way to position a seal outer case and wear sleeve relative to each other, insuring that there is proper axial space for the axial elastomeric lip in case one element is accessible to the mounting tool, and to provide a labyrinth with extremely small clearance and minimum variation in such clearance due to tolerance stack-up.
By cassette seals as used herein is meant a seal containing two separately manufactured elements installed and used as a unit in a given application; cassette seals include a composite seal element and a wear sleeve element. With this type of seal, the composite seal element includes a mounting flange and a seal body attachment flange with an elastomeric seal body bonded thereto and including surfaces adapted to engage a mating part along a generally circular locus to form a seal band. In most ordinary seals, the part mating with the seal comprises a shaft or other machine part. In the cassette seal, the cooperating sealing surface is instead formed on a second element, usually termed a wear sleeve. This element normally includes a cylindrical surface cooperating with a seal band-forming portion of the radially acting seal body, and one or more radial flanges that, among other things, serve an excluder, labyrinth or similar protective function.
Some of the advantages of a two-element seal are well known. For example, a seal assembly wherein both elements are made by the same manufacturer can be pre-sized and pre-fit so that there will be no question about proper functioning upon installation. From an administrative or quality assurance standpoint, both elements are made by the same entity and accordingly, elimination of possible defects and accountability for possible imperfections is rendered relatively simple and straightforward. With most two-element seals of the type with which the invention is concerned, therefore, sealing conditions can be carefully controlled so that the composite seal and the wear sleeve elements cooperate fully and operate as designed, free from malfunctions that might otherwise be caused by misapplication or mis-installation of the product or the like.
However, seals of type in question, although advantageous in respect to the problem of accurate, reliable and generally foolproof sealing, have a few possible drawbacks. One of these relates to the manner in which the seal is actually installed in practice, bearing in mind that this is done on a mass production basis. In this connection, it will be appreciated that although the cost of an oil seal is very small in relation to the value of the mechanism being protected, its potential for damage or dissatisfaction is large.
If a seal fails, there is not only the expense of seal replacement, but also the cost of labor. Considering that many seals are normally extremely inaccessible in use, replacement labor is a significant expense. If the seal failure has occasioned damage to the sealed part, then there will be a still further expense. Therefore, virtually completely foolproof installation of a seal is necessary to insure that it will perform according to expectations. Thus, one or more properly designed and installed low cost seals may insure extended service life for expensive elements such as wheel hub assemblies or even engines, transmissions or the like.
In this connection, installation of two-element seals has created a problem in many applications. In order to achieve proper installation, the two elements need to be spaced axially apart to a relatively exact degree. One way in which this may be achieved is to separately insert one element and subsequently insert the other one, measuring the distance between the two by a separate operation. In some instances, a specialty tool is provided with seal-engaging surfaces that are offset by a distance equal to the desired clearance which is intended to remain when installation is complete. However, this approach has some drawbacks, particularly where the flange that is to be engaged by one portion of the tool is obscured by another portion of the seal or by the portions of the housing in which the seal is to be positioned.
In some instances, the seals are constructed in a "unitized" assembly wherein the two elements are pre-assembled and subsequently inserted as a unit into the application. However, the process of installation normally involves transferring force from one part of one element to the other in a manner which leaves parts in contact that are subsequently required to be abraded. This can create a problem during the initial wearing or "bedding in" process undergone by the seal, and in some cases, thereafter.
Moreover, forming the seal in an assembly at the factory requires additional elements, such as snubbers, chaplets or the like to be present and in some cases, various auxiliary flanges or curls are required to be imparted to the elements to insure the proper relative positioning of the seals. Manufacturing seals of this sort therefore involves a greater cost than should be necessary to achieve desirable results.
According the to the present invention, it has been found that a pair of cooperating seal elements can be designed and manufactured in such a way that, upon installation, one part may be made to bear upon the other for the purpose of transmitting an installing force suitable to position both elements of the seal properly and, upon release of that installing force, a flange of one of the elements will, through its own innate resiliency, spring back to an unstressed or fully installed position wherein there is a slight but definite clearance between such part and its companion element.
This does away with the need for abradable snubbers or the like and also insures that the seal will be properly vented upon initial installation. As will be apparent, if there is metal-tc-metal contact between parts that rotate relative to each other, the seal would be initially damaged. Where abradable materials are provided for this purpose, scrap in the form of fine dust or like particles are created and, as pointed out above, the ability to have fresh air circulate in the region of the primary seal lip can be impeded during this process. However, the parts should lie close enough to each other to provide a labyrinth effect.
The prior art having offered products which are capable of improvement in regard to cost and reliability of installation, it is an object of the invention to provide an improved, dual-element excluder seal.
Another object of the invention is to provide a two-element seal, one of which comprises a composite seal element and the other a so-called wear sleeve or companion flange of special design and construction.
Yet another object of the invention is to provide a two-element seal wherein portions of the two elements cooperate with each other during installation to insure a completely reliable installation process.
Still another object of the invention is to provide an excluder seal assembly wherein a portion of a first element transiently engages a portion of a second seal element during installation to transfer axially applied forces thereto, and wherein such portion of the first element springs back upon completion of the installation so as to provide a working clearance between the two elements.
A further object of the invention is to provide a two-element seal assembly which, by reason of design and manufacture, eliminates the need for so-called for pre-unitized construction.
A still further object of the invention is to provide a seal of the cooperating parts or so-called cassette type which is able to be manufactured and installed reliably at low cost and which will deliver consistently outstanding performance in use.
An additional object of the invention is to provide a seal in which, in one form, a radial flange on the wear sleeve engages an axial flange on the composite seal element during installation, and wherein, in another form, the wear sleeve radial flange engages a radial flange extending from an axial or mounting flange surface of the composite seal element during installation.
Another object of the invention is to provide a seal assembly wherein the wear sleeve may undergo rotary motion and have a portion that will serve an auxiliary function such as providing apertures or "teeth" for cooperation with the sending or pickup elements of an anti-lock braking system, electronic speedometer or the like.
Yet another object of the invention is to provide a form of two-element seal wherein the individual elements may be varied somewhat in construction and arrangement and still achieve the desired advantages during installation, namely, the use of one portion of one element to bear against a portion of the other element during installation and to spring back to an unloaded or unstressed position during use, thus providing a labyrinth with a definite space between elements.
The foregoing and other objects and advantages of the invention are achieved in practice by providing an excluder seal having a composite seal element and a wear sleeve element adapted to cooperate with each other, with the seal element including a seal body having portions adapted to engage the wear sleeve element to form a dynamic seal band therewith and a wear sleeve element having a wearing surface in opposed contacting relation to the seal band forming surface on the composite seal element, and further including at least one resilient flange having one surface able to be engaged by an installation tool and another surface adapted to engage a part of the composite seal element on the surface of the flange opposite the surface engaged by the installing tool.
The manner in which the foregoing and other objects and advantages of the invention are achieved in practice will become more clearly apparent when reference is made to the following detailed description of the preferred embodiments of the invention set forth by way of example and shown in the accompanying drawings, in which like reference numbers indicate the corresponding parts throughout.